Endocrine Abstracts

Background: The diagnosis of Adult Growth Hormone Deficiency (AGHD) requires confirmation with a Growth Hormone (GH) stimulation test, traditionally either an Insulin Tolerance Test (ITT) or Glucagon Stimulation Test (GST). These tests are often poorly tolerated, labour-intensive, and may have limited diagnostic accuracy. Macimorelin is an oral Ghrelin receptor agonist that potently stimulates GH release. The Macimorelin Stimulation Test (MST) is well-tolerated and highly accurate in diagnosing AGHD, with sensitivity and specificity comparable/superior to ITT, the current gold standard test. MST is less resource-intensive (shorter test duration with fewer blood tests). We piloted MST as an alternative to GST for suspected AGHD.

Results: 24 patients (13 female; 11 male; average age 50y; range 19-76y) underwent MST for AGHD evaluation between January and August 2024. All tests were completed successfully, with no inconclusive results. The average patient stay for MST was 1.5-2 hours, compared to a minimum 5-6 hours for GST. Average patient satisfaction scoring for MST was 8.8/10 (n = 11). 2 of 3 patients who had previously undergone GST rated MST more favourably. The other found them equivalent. All adverse events (n = 8; 32.3%) were mild and consistent with the known safety profile of Macimorelin, not requiring post-test care. Compared to GST, MST was found to be less demanding of staff and endocrine bedspace time, allowing multiple tests to be booked per day, thus improving access and reducing waiting times for ADGH testing and other endocrine investigations.

Conclusions: Macimorelin Stimulation Testing represents a valuable alternative to ITT and GST for the diagnosis of AGHD. Our pilot confirms that it is well-tolerated, highly accurate, and less resource-intensive than ITT or GST. The adoption of MST as a first-line test may improve patient experience, optimise endocrine testing unit operations, and enhance access to AGHD diagnosis.